how to export out keymaps?
Blender stores the keymaps in a python script file, hence the .py extension. What you are looking at is Blender's internal file browser. Just give your keymap a name and browse to where you want to export the keymap and press "Export Key Configuration..." 

If you ever want to revert back to that exported keymap, simply press the Import... and browse to the .py file you previously saved. Voila.